I've had a 120ltr tank for several years but non of my fish have lived to the ripe of age of two!!! I have just restocked my tank with lots of plants, a new filter, two fantails that have been in it for three weeks, another fan tail and a black moor introduced yesterday along with a very small cold water fish, not a goldfish, which has been resident for several years. ( He is non agressive.)

As the fish are still small 120 ltr will be fine for the moment but should I upgrade as they get bigger? I do a gravel clean every two weeks, amounting to a household bucket full (about 10%) plus top up of evaporated water and feed the fish every other day. Is this about right to encourage a long life or should I feed daily and soak the dry food before hand. I also feed blood worms and cucmber on a weekly basis.

I'll just go right ahead and assume that you never cycled your tank, or you're not providing adequate maintenance. Your current tank should not have any more fish than three goldies, since you wrote in liters, thing 40-50 liters per fish. Even if they're still small, the tank is over stocked, because they still create waste that you can't see! Just by breathing they excrete ammonia.You should always change at least 50% every week, having such an overstocked tank. Do you have a test kit? So that you could check parameters such as pH, ammonia, nitrite and nitrate?? It's important that you do this the first few weeks/months at least until you'll know about how much waste to expect in the tank after a certain amount of time after a water change. Your best bet would be testing it weekly BEFORE the water changes, and later at least once every two weeks/month.

You could always buy sinking pellets for your goldfish, that way you wouldn't have to worry about soaking them, and they would have lots of fun digging for the leftovers in the gravel